The present invention relates to a new and improved construction of measuring apparatus for determining the position of a roller apron in a continuous casting installation comprising an at least partially curved roller apron or strand guide arrangement, wherein there can be applied to measuring points of the roller apron plumb bobs or lines which project the position of the measuring points in the x-axis or z-axis, respectively, into a substantially horizontal measuring plane.
During the continuous casting of metals, especially steel, an exact alignment of the position of the roller apron or strand guide arrangement in the secondary cooling zone in an absolute requirement for the good quality of the cast product. Yet, the roller apron or strand guide assembly is however subjected during the casting operation, especially when working with pours lasting over a longer period of time, to the thermal radiation which oftentimes alters the geometry of the roller apron. This can result in reduction of the quality of the cast strand by the formation of fissures, especially when casting specialty steels.
During the assembly of the continuous casting installation, especially in the case of a slab-and large bloom-casting installation, there have become known to the art conventional measuring devices for the alignment of the roller apron, such as levelling devices, plumb bobs, bubble levels, radian calibers and so forth. Additionally, after placing the plant into operation it is appropriate to carry out at certain time intervals a post-checking of the roller apron. When using radian calibers or gauges it is possible to control only relatively short roller apron sections. It is not possible to obtain any information regarding the accuracy of the path of the roller apron through a number of sections, and equally, it is not possible to obtain any information concerning the position and dimensional stability of the base frame and the foundation with such calibers.
There is already known to the art a measuring device for the mounting and the operation of arc-type continuous casting installations which consists of a gauge pivotably arranged at the center of the circular arc. This gauge is equipped with adjustable control pins which can be adjusted to the radius of the guided strand surface. With this apparatus it is possible to exactly assemble and measure the arc-shaped path of the roller apron, especially the fixed side. However, it is not possible to control with the use of such measuring apparatus a completely assembled, operationally-ready roller apron equipped with spray nozzles, hoses, adjustment cylinder and so forth, because there is absent the necessary accessibility to the roller apron elements. During the casting operation there is likewise not possible a measurement for the same reasons and additionally due to the operating conditions and the danger of accidents. Moreover, the measuring apparatus when working with slab- and bloom- continuous casting installations operating with conventionally 8 to 15 meter casting radius is cumbersome and therefore can only be moved with a lifting mechanism, and furthermore, is exposed to large dimensional deviations in its length in the presence of temperature fluctuations.
Furthermore, during the installation of continuous casting plants it is conventional to apply plumb bobs at measuring points of the roller apron. These plumb bobs or lines project the positions of such measuring points into a horizontal measuring plane where the reference value or dimension or its deviations can be determined in the x-axis or z-axis respectively. By means of levelling devices is possible to determine by carrying out angle or trigonometric measurements the positions of the measuring points in the y-axis. Such measurements require a great deal of time during the assembly of the casting installation. When the installation has been assembled into a condition where it is ready for use then the roller apron is surrounded by spray tubes, coverings, hoses, adjustment cylinders and so forth so that it is only possible to measure-out the roller apron by carrying out indirect measurements. A rapid and exact checking of the machine geometry during repair steps or a permanent monitoring during the casting operation and during standstill times, i.e. during the hot- and cold state of the machine, is not possible with the aforementioned measuring devices.